Multiprocessing execution environments, where several independent sequences of instructions execute concurrently within separate or shared memory spaces, support a powerful paradigm for attacking many types of computational problems and for using multiprocessor systems efficiently. The threads of a multithreaded program, and cooperating processes that do not have the shared memory space that characterizes threads, often need to synchronize their activities to ensure correct operation. The synchronization is usually accomplished through operations on synchronization primitives, also called synchronization objects or synchronization resources (“resources” in short) provided by an operating system or other execution environment. Mutexes, semaphores, and events are examples of synchronization primitives or resources that provide various synchronization semantics.
Analyzing the operation of a multithreaded program can be a daunting task. Developing, extending and debugging a complex application may be difficult because of intricate relationships between the synchronization operations of various threads. Furthermore, because the precise order of thread operations may vary from run to run and from system to system, synchronization errors (which often manifest as deadlocks or “hangs”) may not occur frequently enough to identify and correct the underlying error.
A method of detecting potential synchronization errors even when no actual deadlock occurs may serve as the basis of a useful analytical tool for software developers.